The present invention relates generally to power line communication systems and, more particularly, to a wireless field configuration terminal for communicating with a power line communication device without the requirement of direct physical or electrical connection thereto.
Power line communication systems have been developed for the purposes of permitting a central communication station to transmit and receive messages from remote devices. In the typical application, such as an electric utility system, a multiplicity of consumers is provided with power line communications devices that enable a central station of the electric utility to transmit messages to each of the consumers devices and receive messages therefrom. In a typical application, the central station would transmit load shed commands or requests for energy consumption data from the remote terminals and receive transmissions from the remote terminals relating to the electrical energy consumption of the associated residence or acknowledgement that a load shed command has been executed. The remote power line communication devices located at the consumer's residence can be an electrical energy meter or a load management terminal. Although some load management terminals are provided only with the ability to receive messages, many applications employ load management terminals and electrical meters that have the capability of two-way communication with the central station.
U.S. Pat. No. 3,911,415, which issued on Oct. 7, 1975 to Whyte, discloses a distribution network power line carrier communication system for linking individual power consumers with a central station, including the power distribution network between a distribution substation and the customer locations. U.S. Pat. No. 3,967,264, which issued on June 29, 1976 to Whyte et al, discloses a distribution network power line communication system which is divided into addressable communication zones defined by repeaters that are located at the distribution transformers of the distribution network. U.S. Pat. No. 3,942,170, which issued on Mar. 2, 1976 to Whyte, discloses a distribution power line carrier communication system for providing automated distribution functions. U.S. Pat. Nos. 3,911,415, 3,967,264 and 3,942,170 are hereby incorporated by reference.
U.S. Pat. No. 4,302,750, which issued on Nov. 24, 1981 to Wadhwani et al, discloses a data communications system for conveying load control commands, power usage data and other data on electrical power lines. It utilizes a remote module for reading the power usage meters and controlling loads. U.S. Pat. No. 4,382,248, which issued on May 3, 1983 to Pai, discloses a remote device for receiving communication signals carried by the phase conductors of a multi-phase power distribution network communication system. The device includes a circuit for independently receiving each of the communication signals carried by the phase conductors. U.S. Pat. Nos. 4,302,750 and 4,382,248 are hereby incorporated by reference.
The signals that are transmitted on the power lines in a power line communication system can be modulated by a number of techniques. One particularly useful technique is a phase-keyed modulation system that utilizes a carrier signal which is modulated with a baseband data message comprising digital data. In a typical application, the carrier signal has a frequency of approximately 12.5 kilohertz, and this carrier signal is modulated with the baseband data message. The phase shift-keyed modulation can be accomplished by utilizing an exclusive-OR device having the carrier signal and the baseband data message as its inputs. The modulated signal is then amplified and then injected onto the power line.
U.S. Pat. No. 4,323,882, which issued on Apr. 6, 1982 to Gajjar, discloses a method and apparatus for inserting carrier frequency signal information onto distribution transformer primary windings. Using this apparatus, power line carrier frequency signals are provided at a distribution transformer primary winding by controlled current injection onto the neutral and phase conductors of the distribution transformer secondary winding circuit. When the modulated signal is received by either a remote device or the central station, it must be demodulated before the transmitted message can be decoded. U.S. Pat. No. 4,311,964, which issued on Jan. 19, 1982 to Boykin discloses an apparatus and method for demodulating phase shift-keyed messages. It includes sequentially processing plus and minus polarity samples of plural carrier segments occurring within each carrier data symbol. U.S. Pat. Nos. 4,323,882 and 4,311,964 are hereby incorporated by reference.
As discussed above, the remote devices of a power line communication system can be either load management terminals or electrical meters. U.S. Pat. No. 4,130,874, which issued on Dec. 19, 1978 to Pai, discloses a load management terminal having plural selectable address formats for a power line communication system. U.S. Pat. No. 4,130,874, issued on Dec. 19, 1978 to Pai, discloses a load management terminal that is addressable by alternate codes. U.S. Pat. No. 4,402,059, which issued on Aug. 30, 1983 to Kennon et al, discloses a load management terminal that is utilized as an end device in a utility's distribution network communication system. It comprises a power line coupling unit for connecting the load management terminal to the power distribution network. It also comprises a signal receiver and conditioning unit that produces a command signal in response to a receive communication signal from the power line communication system. U.S. Pat. No. 4,429,366, which issued on Jan. 31, 1984 to Kennon, discloses a microprocessor-based load management terminal with reset capabilities. A microprocessor performs load control functions in response to command signals that are produced by a signal receiver and conditioning unit.
Many other types of apparatus and methods are known to those skilled in the art of power line communication systems. For example, U.S. Pat. No. 4,379,284, which issued on Apr. 5, 1983 to Boykin, discloses a coherent phase shift keyed demodulator for power line communication systems, U.S. Pat. No. 4,355,303, which issued on Oct. 19, 1982 to Phillips et al, discloses a receiver for distribution network power line carrier communication systems, U.S. Pat. No. 4,250, 489, which issued on Feb. 10, 1981, to Dudash et al, discloses a distribution network communication system having branch connected repeaters and U.S. Pat. No. 3,925,728, which issued on Dec. 9, 1975 to Whyte, discloses an induction watthour meter for power systems transmitting carrier communication signals.
Occasionally, it becomes necessary for an electric utility to examine the operation of a particular remote device or alter the operational data contained therein. In a typical application, this requires an operator to travel to the residence with which the device is associated and perform various procedures in order to determine if the device is operating properly or, alternatively, to change the operational instructions or data contained within the device. This second procedure would generally relate to the alteration of messages or data stored in a microprocessor within the remote device.
U.S. Pat. No. 4,467,314, which issued on Aug. 21, 1984 to Weikel et al, discloses a field configuration terminal (FCT) that provides a means for efficiently testing and assigning addresses to load management terminals in the field. It describes a combination field configuration and test terminal which can be plugged into a load management terminal in the field. The combination terminal is coupled to the power line through the connection to the load management terminal and generates a separate set of test commands for each type of load management terminal. These test commands are transmitted over the power line for execution by the connected load management terminal. This set of test commands comprises commands that instruct the load management terminal to accept and store an address value received over the power line as its new unique address. Other types of commands and instructions can also be transmitted to the load management terminal during these configuration and testing procedures. U.S. Pat. No. 4,467,314 is hereby incorporated by reference.
Field configuration terminals (FCT's) such as the one described in U.S. Pat. No. 4,467,314 are generally designed to be implemented in one of two ways. First, the associated load management terminal (LMT) can be provided with a socket into which a plug of the FCT can be inserted. In one particular application, the plug is provided with 28 pins through which the FCT can obtain both power, for its operation, and communications signals. When this methodology is used, the receptacle is generally formed as a part of the load management terminal's base. In customary designs of this type of load management terminal, the receptacle is connected in electrical communication with the power line in such a way as not to consume electrical energy for which the consumer would be charged. A major disadvantage of this type of load management terminal is that the receptacle, or socket, is part of the load management terminal's base. This not only increases the cost of the load management terminal, but also provides a potential safety hazard to the consumer. Furthermore, since the receptacle is accessible, tampering can be difficult to prevent.
Another approach for connecting a field configuration terminal (FCT) to a load management terminal (LMT) includes the use of a conventional electrical receptacle in the resident's house wiring system. A conventional electrical plug can be provided with the field configuration terminal and it can be plugged into the conventional electrical receptacle. This procedure would provide electrical power for the operation of the field configuration terminal and also provide a coupling between the FCT and the power line. The FCT could then inject modulated power line communication signals into the house wiring system for receipt by the load management terminal. This procedure presents two disadvantages. First, it utilizes the electrical energy of the consumer, for which the consumer will be charged. Although a typical application of a field configuration terminal utilizes a very small amount of electrical energy, electric utilities generally prefer to refrain from this approach as a matter of policy. Another disadvantage to this approach is that not all consumer residences have electrical receptacles that are proximate the load management terminal. This fact could make the use of a conventional electrical receptacle at the residence inconvenient.
In view of the above discussion, it should be apparent that a field configuration terminal which does not require physical contact with the load management terminal would provide significant advantages to an electrical utility that employs a power line communication system with a plurality of remote devices.
The present invention provides a field configuration terminal that enables messages to be transmitted to and received from a load management terminal, or electrical meter, without the requirement of physical or electrical contact between the field configuration terminal and the load management terminal. The present invention comprises a multi-turn conductor that is configured in the shape of a toroid. The toroid is shaped to fit around the load management terminal.
The field configuration terminal of the present invention comprises a means for modulating a carrier signal with a baseband message. In a phase shift-keyed modulation system, an exclusive-OR gate can be used to provide this modulation. The exclusive-OR gate has two inputs, one connected to a carrier generator and the other connected to a source of the baseband data message. The carrier generator, in a typical application of the present invention, provides a carrier signal of 12.5 kilohertz and the base-band data message is provided by a microprocessor that formulates the message and sends it to the input of the exclusive-OR gate.
The present invention also comprises an amplifier that has, as its input, the output of the exclusive-OR gate. The output of the amplifier is operatively associated with the conductor that is formed into the shape of a toroid with a multiplicity of turns.
The present invention also comprises receiver circuitry that receives a sinusoidal signal from the toroid, passes the signal through a high pass filter, hard limits the signal and sends the signal to an input of a demodulator. In a preferred embodiment of the present invention, the demodulator is incorporated within a microprocessor.
In some applications, the load management terminal has a magnetically actuated switch that is used by its microprocessor to determine the validity of incoming signals. More particularly, the magnetically actuated switch provides a signal that is indicative of the presence of a field configuration terminal. The actuation of the switch within the load management terminal causes a signal which permits certain procedures to be used to affect the data and instructions within the load management terminal's microprocessor. In order to implement this procedure, the toroid of the present invention can be provided with a magnet attached thereto at an arcuate position coincident with the magnetically actuated switch of the load managment terminal.
The present invention also comprises a battery operated power supply that provides a direct current for the operation of its microprocessor and control logic. This power supply also provides a direct current source for the amplifier.
The present invention provides a portable field configuration terminal that requires no physical or electrical connection with a remote load management terminal. It is capable of transmitting messages to the load management terminal and receiving messages therefrom. Amplified signals passing through the turns of the toroid induce a fluctuating magnetic field that induces current signals in the components, wires and printed circuit board runs of the load management terminal. These induced current signals are received by the load management terminal's microprocessor and processed as if they were transmitted from either a remote transmitter or a field configuration terminal electrically connected to the power line. The toroid of the present invention also receives signals transmitted from the load management terminal. When the load management terminal transmits a message, the resulting magnetic fields induce current signals in the turns of the toroid and these signals are received by the receiver circuitry of the present invention and subsequently demodulated by the demodulator within its microprocessor.